Creating Expressions

Dialogue Manager reads information from an external file and writes information to it. This section describes the command -WRITE. For information on -READ, see Supplying Values for Variables.

An expression consists of variables and literals (numeric or alphanumeric constants) that are combined arithmetically, logically, or in some other way to create a new value.

Dialogue Manager has few restrictions on creating expressions. However, keep in mind that an expression cannot exceed 40 lines or 16 -IF...THEN...ELSE commands.

Arithmetic Expressions

Reference:

Guidelines for Using Arithmetic Expressions

An arithmetic expression is:

A numeric constant, for example, 1.

Two variables joined by one of the following arithmetic operators:

Operator

Meaning

+

Addition

-

Subtraction

*

Multiplication

/

Division

**

Exponentiation

Operator	Meaning
+	Addition
-	Subtraction
*	Multiplication
/	Division
**	Exponentiation

An example is:

&DELIVER_AMT / &OPENING_AMT

Two or more arithmetic expressions, joined by one of the operators in the preceding list. An example is:

(&RATIO - 1) ** 2

A compound expression or function that gives an arithmetic result. See Using Functions for more information.

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Example: Using Arithmetic Expressions

Following are three arithmetic expressions used in the command -SET:

-SET &COUNT = 1;
-SET &NEWVAL = (&RATIO - 1) ** 2; 
-SET &RATIO = (&DELIVER_AMT * 100) / (&OPENING_AMT);

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Reference: Guidelines for Using Arithmetic Expressions

Keep the following in mind as you create arithmetic expressions:

If you attempt to divide by 0, Dialogue Manager sets the result to 0.

Arithmetic operations are performed before logical operations, in the following order:

Operator

Meaning

**

Exponentiation

/ *

Division and multiplication

+ -

Addition and subtraction

Operator	Meaning
**	Exponentiation
/ *	Division and multiplication
+ -	Addition and subtraction

For operations on the same level (for example, division and multiplication), the evaluation is performed from left to right.

An expression in parentheses is evaluated before any other expression.

Values for local and global variables (amper variables) are stored internally as character strings, including numeric values. If a calculation is performed on an amper variable, the variable is first converted from a character string into a numeric. After the whole result is calculated, the result of arithmetic operations with numeric fields is truncated to the integer field. Finally, the result is converted back into a character string.

Alphanumeric Expressions

How to:

An alphanumeric expression is:

A literal enclosed in single quotation marks, for example 'Smith John'.
A logical expression that yields an alphanumeric result.
A function that yields an alphanumeric result.
Two or more alphanumeric variables or literals combined into a single string. See How to Concatenate Alphanumeric Variables and Literals for the syntax and an example.

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Syntax: How to Concatenate Alphanumeric Variables and Literals

 
variablename = {alphaexp1|'literal'} concatenation 
{alphaexp2|'literal'} [...]

where:

variablename

Is the name of the variable assigned to the result of the concatenation.

alphaexp1, alphaexp2

Are local or global variable that forms part of the concatenation.

literal

Is a literal that forms part of the concatenation. It must be enclosed in single quotation marks.

concatenation

Is one of the following symbols:

||

Indicates strong concatenation, which suppresses trailing blanks.

|

Indicates weak concatenation, which preserves individual field lengths, including trailing blanks.

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Example: Concatenating Alphanumeric Variables and Literals

-SET &NAME = &LASTNAME || ',' || &FIRST_INIT;

If &LASTNAME is equal to Doe and &FIRST_INIT is equal to J, &NAME is set to:

Doe,J

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Syntax: How to Use Date Functions

System-supplied date functions enable you to calculate the number of days between start and end dates, including leap years. The date format must be either alphanumeric or integer.

 
datefield (begin, end)
-SET &LOSRV = YMD(&HIRE_DATE,040101);

where:

datefield

Is one of the following:

YMD is the number of days between two dates stored as year-month-day (for example, 850522).

MDY is the number of days between two dates stored as month-day-year (for example, 052285).

DMY is the number of days between two dates stored as day-month-year (for example, 220585).

begin

Is the start date.

end

Is the end date.

In the following example, &LOSRV is set to the number of days between &HIRE_DATE and the literal 040101:

-SET &LOSRV = YMD(&HIRE_DATE,040101);

Logical Expressions

Reference:

Guidelines for Alphanumeric and Logical Expressions

A logical expression contains logical and relational operators and is evaluated to a value that is true or false.

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Example: Forming a Logical Expression

This example shows various elements that are used to form a logical expression. The abbreviation exp stands for expression.

{arithmetic exp|alphanumeric exp} operator1 {numeric lit|alphanumeric lit} OR...
  
expressionoperator2expression 
logical exp {AND|OR} logical exp 
 
NOT logical exp

where:

operator1: Is one of the following: EQ, NE, OMITS, or CONTAINS.
expression: Is either an arithmetic, alphanumeric, or logical expression.
operator2: Is one of the following: EQ, NE, LE, LT, GE, or GT.

The following table defines valid operators (EQ, NE, and so on) used in this example.

Operator	Description
EQ	Tests for a value equal to another value.
NE	Tests for a value not equal to another value.
OMITS	Tests for a value that does not contain a matching character string.
CONTAINS	Tests for a value that does contain a matching character string.
LE	Tests for a value less than or equal to another value.
LT	Tests for a value less than another value.
GE	Tests for a value greater than or equal to another value.
GT	Tests for a value greater than another value.
AND	Returns a value of true if both of its operands are true.
OR	Returns a value of true if either of its operands is true.
NOT	Returns a value of true if the operand is false.

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Reference: Guidelines for Alphanumeric and Logical Expressions

Keep the following in mind:

An alphanumeric literal with embedded blanks or commas must be enclosed in single quotation marks. For example:
```
-IF &NAME EQ 'JOHN DOE' GOTO QUIT;
```
To produce a single quotation mark within a literal, place two single quotation marks where you want one to appear:
```
-IF &NAME EQ 'JOHN O''HARA' GOTO QUIT;
```
A computational field may be assigned a value by equating it to a logical expression. If the expression is true, the field has a value of 1; if the expression is false, the field has a value of 0.
Use OR to connect literals or other expressions. You must also use parentheses to separate expressions connected with OR.
Logical operations are done after arithmetic operations, in the following order:
```
EQ NE LE LT GE GT NOT CONTAINS OMITS
```
```
AND
```
```
OR
```
Separate a collection of test values with OR:
```
-IF &STATE EQ 'NY' OR 'NJ' OR 'WA' GOTO QUIT;
```
In this case, OR and EQ are evaluated at the same level.
Use parentheses to specify a desired order. An expression in parentheses is evaluated before any other expression. For example, the command
```
-IF &STATE EQ 'NY' AND &COUNTRY EQ 'US' OR 'UK' THEN...
```
is evaluated as:
```
IF &STATE EQ 'NY' IF &COUNTRY EQ 'US'...
```
Dialogue Manager then evaluates the phrase OR UK and indicates that it is a syntax error.
To write the command correctly, add parentheses:
```
-IF ((&STATE EQ 'NY') AND (&COUNTRY EQ 'US' OR 'UK')) THEN...
```

Compound Expressions

A compound expression has the following form:

-IF expression THEN expression ELSE expression;

The following restrictions apply:

Each of the expressions may itself be a compound expression, although the expression following -IF may not be a -IF...THEN...ELSE expression (for example, -IF...-IF...).
If the expression following THEN is itself a compound expression, it must be enclosed in parentheses; this rule does not apply to an expression following ELSE.
Compound expressions only have up to 16 -IF commands.

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Example: Using Compound Expressions

If the following example is executed without an input parameter list, the client application receives the message NONE. If it executes with the parameter BANK='FIRST NATIONAL', the client application receives the message FIRST NATIONAL.

-DEFAULTS &BANK = ' '
-SET &BANK = IF &BANK EQ ' ' THEN 'NONE'
-ELSE &BANK;
-TYPE &BANK

The next example uses a compound expression to define a truth condition (1 is true and 0 is false).

-DEFAULTS &CURR_SAL = 900,&DEPARTMENT=MIS
-SET &MYTEST = (&CURR_SAL GE 1000) OR (&DEPARTMENT EQ MIS);
-IF &MYTEST EQ 1 THEN GOTO YES ELSE GOTO NO;
-YES
-TYPE YES
-EXIT
-NO
-TYPE NO

When this code is executed, the client application receives the message YES.

\|\|	Indicates strong concatenation, which suppresses trailing blanks.
\|	Indicates weak concatenation, which preserves individual field lengths, including trailing blanks.